Expansion vessel stuffed, can I fit an 'external'(?) one?

[BigBurner]

even if you were to replace the standard vessel i'd add an external one as well because the expansion vessel, due to the hot water store, is ridiculously small and if you have an average house with 8 rads (i know you have 7) you need an additional one, if you have less rads but they're big then you also need one.

if you can get away with fitting the external vessel i'd do that.

Bed advice. You size it up and add if need be. If a needless expansion vessel was fitted that would take much expansion and reduce the store heat in the thermal store/expansion vessel.

Depending on the internal layout you may want to put in a second PRV in case.

why? the standard pressure relief will still work

You missed the point.

 

[Agile]

Bed advice. You size it up and add if need be. If a needless expansion vessel was fitted that would take much expansion and reduce the store heat in the thermal store/expansion vessel.

What has a bed got to do with it?

The whole point of an expansion vessel is surely to "take up expansion" ?

I dont think that you have copied the brochures very well or are you looking for a new bed?

There are some good bargains in beds and suites at the moment as the retailers are all closing down.

Tony

 

[BigBurner]

The whole point of an expansion vessel is surely to "take up expansion" ?

You clearly do not understand these things. Water expands into the internal vessel against the diaphragm. If it expands against another as well, less primary water is stored in the internal vessel to be heated. Do you now understand?

 

[Agile]

Sadly you have lost the thread! Its about adding an external EXV to replace the function of the internal EV.

The internal EV is failed so the external EV becomes the only one in the system.

The EV in the boiler is retained because its a thermal store.

You did not explain your reference to a bed!

Tony

 

[Agile]

Depending on the internal layout you may want to put in a second PRV in case.

why? the standard pressure relief will still work

If the boiler isolating valves were closed then the filling loop could leak or accidentally get left open.

To prevent this situation a PRV on the heating side will provide protection for less than a £10 and avoid the possibility of a burst radiator costing say £50 for the rad and £1000 for water damage! All for less than 1% of the possible damage the lack of it could cause!

Furthermore the PRV will also mitigate against any problems arising from fitting a tool operated isolating valve on the connection to the expansion vessel.

Tony

 

[baxpoti]

If the boiler isolating valves were closed then the filling loop could leak or accidentally get left open.

Surely even in this ridiculous senario the filling loop would be disconnected anyway.

 

[Agile]

Surely even in this ridiculous senario the filling loop would be disconnected anyway.

I dont know where you live or work but in the London area area where I do some work, 25% of the calls I get are from people who dont even know how to fill their systems.

I see about three removed flexibles each year and thats usually landlords who dont want their tenants over pressurising then system.

Tony

 

[bluefudge11]

I have installed the expansion vessel today - (only a couple of leaks - now cured )
All seems to be well - It took me all day though! (stop sniggering all you plumbers out there !)

I used a PRV for the sake of a few quid thought it was worth it.

Thanks to everyone for their advice - It has been most useful
Cheers
BF

 

[Agile]

I hope you air pressured it correctly as I advised you on the other forum!

Tony

 

[bluefudge11]

Hi Tony
Yes I did as you said and all seems to be fine.
Thanks for your advice and for taking time out to reply
Cheers
BF